July 2, 2012

The power blackout in DC was quick. The storm arrived quickly and took most of us by surprise.

But it was the aftermath that I wanted to ask you about. Wherever there was free “juice” people were plugging in their laptops, cellphones and whatever else needed power.

There was no shyness about using the “juice” at McDonald’s, Safeway or even the mall. It was as if these things are free and use as much as you want.

Do you or your readers have any comments about this issue? Instead of a cup of sugar people now want a kilowatt. This rivals neighbors stealing your Wifi.

Well, personally I think the answer to this is somewhere between “any port in a storm” and de minimis non curat lex. The amount of power consumed by a cellphone or a laptop is quite small, and one presumes that power outlets in public places are there with the idea that they might be used by the public. Just don’t get too greedy — charging a cellphone or a laptop is one thing, plugging in your Leaf overnight is another.

Of course, a modest amount of forethought will make this sort of expedient mostly unnecessary. Here’s a post on generators, and at a much lower level of expense, hand-cranked radios like this one will charge cellphones. I have several big UPS units that will keep a laptop and cellphone going for a long time. An inverter is also a good inexpensive alternate power source. You can also get one of these jumpstarters that doubles as a portable power source.

So while I think it’s okay to charge your laptop at McDonald’s in an emergency, courtesy and good sense dictates that you should do what you can to make such an emergency unnecessary in advance.

UPDATE: Reader James Randolph writes:

The key is to not assume it is free; it is paid for by evil corporate profits. If you don’t like corporations on the good days, don’t rely on them on the bad days. Personally, I love McDonalds and regularly contribute to their profits.

Fair point. And reader Dave Moelling writes:

I read your story about using power at McDonalds ,etc. My first response is that this is OK but a courteous thing would be to buy something (coffee, etc.) when using a commercial venues facilities even if not requested. But it reminded me that the two most prepared companies for disasters are WalMart and Waffle House. (See link). A question to those in the Mid Atlantic, How is waffle house doing?

I’m your reader that installs and services generators, including home-stand-by and portable units.

Further to your advice about generators, UPS’s and inverters, you might want to let your readers know that there are still serious issues with generators and UPS units. Except for the largest and most-sophisticated generators, these two devices do not play well together.

The issue is that the UPS makers have set very-narrow boundaries on the frequency input that their devices will tolerate before calling a fault. They will only tolerate a frequency deviation of perhaps ± 0.5 Hz before they call a defect and disconnect from the input to go on battery power.

In a way, this makes sense, because the utility power frequency is usually incredibly accurate – within 0.1 Hz and usually a lot better than that – and so the UPS makers use the disruption in frequency as a warning that utility power is going out.

But most generators in the size class we are talking about cannot maintain output frequency that accurately. Electronic governors (which control engine speed and so output frequency) are only found on one or two larger, high-end generators at present, most still use mechanical governors, which are less-precise. And even with an electronic governor, most of these generators do not have enough rotor inertia to maintain engine speed (= frequency) during the startup of large load, like a refrigerator or well pump.

Generators based on inverter technology are better because they synthesize their output frequency electronically and so do not depend on engine speed. However, inverter technology is presently restricted to very small generators, not suitable for backup power for a whole house.

Users should be aware that, for most generators that are likely to be found in a domestic application, when the power goes out, any UPS’s will likely switch to battery backup and stay there, even if the generator is energized and providing input power. Since most UPS’s have only limited backup capacity, they will be quickly exhausted and will not be replenished form the generator input.

For those with no generator, or using a portable generator intermittently, for low-level charging needs, like phones and laptops, the best solution is a 12V auto battery and a miniature inverter. The battery can be charged in so many different ways (from a car, from a charger running off a generator, from a lawnmower, from a solar panel, the possible ways are endless) and even a small lead-acid battery (like a lawn-tractor battery) has more-than-enough capacity to charge many cell-phones and laptops before requiring a fresh charge.

Good advice. And another reader points out: “The McDonalds that don’t want people to use their power have already capped the outlets in the public areas. Some newer McDonalds have extra outlets as a convenience for customers.”